Extrusion lubricants



United States Patent 3,379,642 EXTRUSION LUBRICANTS Morris L. Nielsen,Dayton, and Roger M. Niemi, Hamilton, Ohio, assignors to MonsantoResearch Corporation, St. Louis, Mo., a corporation of Delaware NoDrawing. Filed July 7, 1967, Ser. No. 651,686 6 Claims. (Cl. 252-29)ABSTRACT OF THE DISCLOSURE An improvement in the process of metalextrusion in which a composition comprising a reaction product ofmelamine and a phosphorus (V) acid or anhydride is used as a lubricant.A laminar lubricant such as graphite may also be present.

BACKGROUND OF THE INVENTION This invention relates to the extrusion ofmetals and alloys having melting points above 1000 C., and particularlyto means of lubricating such metals and alloys in conjunction with theirpassage through extrusion dies. Extrusion of metals such as copper,lead, zinc or aluminum is a well-known commercial operation. Manyconfigurations of shapes and tubing have been made available as thistechnology has advanced over other methods of metalworking includingcasting, machining, forging, rolling, etc. Certain other metals oralloys having higher melting points, especially above 1000 C., have beenless amenable to extrusion so that for them this method has been slow indeveloping. Such metals as steel, molybdenum, tantalum, tungsten, andsuperalloys require very high temperatures and pressures for extrusionand as a consequence the extruding die issubjected to considerablefriction. Not only does this friction increase the amount of energynecessary to effect the extrusion, but it shortens the operating life ofthe die through erosion and wear. Equally important, it often results ina poorly extruded metal piece having a rough surface with scratches,pits, cracks, laps, tears and gouges. Many attempts to solve thisproblem have been made in the past, principally through extrusion aidsor lubricating materials such as glass or graphite. In U.S. Patent2,538,917 issued Jan. 23, 1951, to I. Sejournet et al. and in US. Patent3,181,324 issued May 4, 1965, to D. Labino, various forms of glass aredisclosed as extrusion lubricants. In US. Patent 2,757,138 issued July31, 1965, to A. Clatot et al., graphite is shown in combination with acombustible organic substance such as sawdust and a higher metal oxide.

These various methods do not yield entirely satisfactory results. Theglass may not be sufiiciently softened in the short contact time that itis exposed to the hot metal, so that there may result occlusions ofglass in the metal, or surface defects due to uneven lubrication andexcessive wear of the die. When greases are used, the contact of hotmetal with organic substances may lead to undesired carbides and surfacehardening by carburization.

vWhen graphite is used alone, extrusion is usually unsatisfactory, dueto failure of the solid non-fusible graphite toflow and replenish thefilm of lubricant between the die and workpiece. Graphite alone suffersfrom the further disadvantage that it has high thermal conductivitywhich hastens the transfer of heat from the hot billet to the coolerdie. This results in two undesirable effects: the workpiece is cooledand the die is heated.

Our present invention overcomes these and other problems.

SUMMARY This invention relates to an improvement in the method ofextruding a metal workpiece, wherein the improvement "ice comprisesapplying to the surface of the workpiece a composition comprising areaction product of melamine and a phosphorus compound selected from theclass consisting of a phosphorus (V) acid and phosphorus pentoxide. Thecomposition may also include a laminar lubricant selected from the classconsisting of graphite, molybdenum disulfide, boron nitride andmetal-free phthalocyanine.

The melamine phosphates prepared from melamine and various phosphorusacids, e.g. ortho-, pyro-, or metaphosphoric acid are well-knowncompounds. Thus, there are melamine orthophosphate, C H N -H PO melaminepyrophosphate, (C H N -H P O melamine metaphosphate, C H N -HPO etc., asreported in Chemical Abstracts 42, 7781h.

By heating melamine with phosphorus pentoxide in a ratio of 2 to 4 molesof melamine to one mole of phosphorus pentoxide at 300500 C., there isobtained a product disclosed in US. Patent 2,544,706 issued Mar. 13,1951, to I. E. Malowan. We have found that these materials soften ormelt at high temperature, often with decomposition, and are transformedto a viscous, fluid or partly fluidstate. For example, the melamine-P 0composition becomes soft and tacky about 900-1000" C.

It is an object of the invention to provide a lubricant formetalworking. It is a further object to provide a lubricant for theextrusion of metals having melting points above 1000 C. It is still afurther object to provide an improvement in the process of extrudingmetals in which a composition comprising a reaction product of melamineand a phosphorus (V) acid or anhydride is used as a lubricant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the extrusion of metalshaving high melting points, e.g. above 1000 C., it is common practice toemploy a 1500 to 2500 ton horizontal extrusion press, see for example,Extrusion of Steel, by D. A. Edgecombe, Journal of Metals, vol. 13, page211, 1961. The die may yield simple or complex shapes, e.g. rods,channels, etc., or may in conjunction with a mandrel yield tubing. Thedie maybe made of a hardened tool steel, and may be coated, eg with A1 0or ZrO In operation, the billet of metal to be extruded is heated to theextruding temperature, which varies with the metal but may be in therange 11-O02000 C. The die is generally preheated to 450550 C., toprevent chilling the workpiece. The die lubricant is inserted and thenthe hot billet. The ram then moves forward at a speed of 5-6 inches/sec. and the workpiece assumes a cross-section corresponding to that ofthe die. In the present invention, the improvement lies in the dielubricant. The following examples illustrate certain specificembodiments of the present invention.

Example 1 Typical formulations which we have found useful as extrusionlubricants are shown in Table 1. The melamine reaction products may beused alone or in combination with laminar lubricants such as graphite.The compositions used in the present invention are prepared by firstcomminutingor crushing the individual components to a finely dividedstate, e.g. passing a 20 mesh sieve, then thoroughly mixing thecomponents in the desired proportions. The compositions may be used in apowdered form, e.g. by scooping into a mold having a die located at oneend, thereafter ramming the heated billet in contact with the powder andthence through the die; or may be used more efliciently by molding thecomposition first in a pellet or disc shape which is then positionedacross the die opening so that the billet is rammed directly against itand thence through the die. Other methods of applying the composition toeither the die or the workpiece may be employed, with the objective ofinterposing the composition between the surface of the die and theworkpiece so that the composition serves to lubricate the die while themetal is being extruded. In the preparation of pellets or shaped forms,binders such as sodium silicates, animal TABLE l.TYPIGAL FORMULATIONSUSEFUL AS EXTRUSION LUBRICANTS Composition, Weight percent Formulations,Components A B C D E F Melamine orthophosphate (1 :1) 100 67 Melamine-Pcomposition of U.S. Patent 100 67 50 33 2,544,706. Graphite 33 33 50 67Coefficient; of Friction at l,100 C 0.1 0.02 0.12 0. 02 0. 02

or vegetable glues, casein resins, polyvinyl chloride, polyinch thickand pushed against the face of the die. vinyl acetate, polyurethanes,epoxy cements, etc., are Billets of 4340 steel were heated to about1150" C., useful for bonding the pressed composition into a suitably inan inert atmosphere induction furnace and were transstrong form.Suflicient binder for this purpose, usually not ferred to the extrusionpress. over 5% by weight of the total composition, may be The results ofextrusions with two compositions as mixed with the composition withoutadversely affecting its lubricants are shown in Table 2. lubricatingproperties. Likewise, mold release agents such TABLE2 EXTRUSION OF 4340STEEL USING EXTRUSION as stearic acid may be present, usually to theextent of LUBRICANTS not 5% by Weight- Conditions, Results, Not only arethe melamine reaction products useful Composit on F o Tablel m SpeedExtruded lubricants per se, but by virtue of their softening and (L/Sec)Surface melting characteristics they may be used with and do 0 yh i p pflr p u 5-5 i enhance the usefulness of laminar lubricants. While we ggfi gifffhffffifhhfi g8 53;, do not have a complete understanding of themechanism by which these desirable results are achieved, we postulate Ii to b understood that l h h invention h that the melamine reactionproducts act as a matrix or b d ib d i h ifi reference to particular hdispersion medium for the laminar lubficahts- We have bodiments thereof,it is not to be so limited since changes found that intim e miXhlreS 0fthe melamine-P205 and alterations therein may be made which are withinthe POsition and graphite become pasty at aboh'E 900-1000 full intendedscope of this invention as defined by the C., and we therefore presumethat under the extrusion appended i conditions this combination flowsand replenishes the What We l i i lubricating film between the metalsurfaces. In this way 40 1 In a method f extruding a metal workpiece h hthe combination surprisingly produces a superior result a i animprovement which comprises l i to the t0 obtained either componentalone. For the urface of the and the workpiece a omposition com P p ofthis invention the h hlbncaht may h prising a reaction product ofmelamine and a phosphorus Prbseht t0 the extent of 90% y Welght of thec011113051" compound selected from the class consisting of a phostioh;however, the Preferred pg is p to a maximum of phorus (V) acid formed atabout the temperature of 70% y Whight of the position. 0-300 C. andphosphorus pentoxide formed at about Example 2 the temperature of 300500 C. 2. The method of cla1m 1 111 which the reaction prod Thecoefficrent of friction for these lubrlcants was deuct is melamineorthophosphate termined in a TRW test machine as follows. A rotating Themethod of claim 1 in which the reaction prod member heated to about 4500and a sfahohary uct obtained by heating 2 to 4 moles of melamine withone ber heated to 1100 C., were held against each other mole ofphosphorus pentoxide at 300 to 5000 under about 5000 p.s.i. pressure.The lubricant was ap- The method of claim 1 in which the composition Pbetween these members and the lecelemhoh of the includes a laminarlubricant selected from the class conrotating member measured. Therotating member c ni m f graphite, molybdenum disulfide, boron nitride,sisted of H- 21 tool steel simulating a steel die the staand metahheephthalocyanhm tionary member was molybdenum-0.5% tltamum. Th 5. Themethod of claim 4 in which the reaction product preheated steel piecewas inserted in a cylindrical cavity is melamine orthophosphate and thelaminar lubricant is in the center of a rotating flywheel; the lubncantwas apa hite, the graphite being present in the ran e of 2 to plied; andthe preheated stationary member was dropped 70% by weight of thecomposition a in on top of the lubricated steel piece. The motor driveThe method of claim 4 in which the reaction Prod was removed h theflywheel and Pressure h uct is obtained by heating 2 to 4 moles ofmelamine with mediately applied to the exposed end of the stationary onele of phosphorus pentoxide at 300 to 500 C., memberh angular ve'locltyof the flywheel was h and the laminar lubricant is graphite, thegraphite being corded until it stopped. A plot of the angular velocitypresent in the range of 2 to by weight of the against time gavesubstantially a straight line whose slope position was proportional tothe coefiicient of friction. The coeffi- References Cited cients offriction obtained for old, established materials were acceptably closeto values reported in the published UNITED STATES PATENTS literatur 702,544,706 3/1951 Malowan 260249.6 Data for useful compositions of thepresent invention 3, 13,024 10/1965 Blake et al. 252-25 are shown inTable 1. 3,265,617 8/1966 Allen 252-25 Example 3 DANIEL E. WYMAN,Primary Examiner.

Extrusions were performed on a 700 ton horizontal ex- I. VAUGHN,Assistant Examiner.

